A functional fluid is a term which encompasses a variety of fluids including, but not limited to, tractor fluids, automatic transmission fluids, manual transmission fluids, hydraulic fluids, power steering fluids, fluids related to power train components and fluids which have the ability to act in various different capacities. It should be noted that within each of these fluids such as, for example, automatic transmission fluids, there are a variety of different types of fluids due to the various transmissions having different designs which have led to the need for fluids of markedly different functional characteristics. One type of functional fluid is generally known as a tractor fluid which can be used in connection with various types of tractor equipment in order to provide for the operation of the transmission, gears, bearings, hydraulics, power steering, mechanical power take off and oil immersed brakes of the tractor.
The components included within a functional fluid such as a tractor fluid must be carefully chosen so that the final resulting fluid composition will provide all the necessary characteristics required and pass a variety of different types of tests. In general, a tractor fluid must act as a lubricant, a power transfer means and a heat transfer means.
Tractor fluids have a number of important specific characteristics which provide for their ability to operate within tractor equipment. Such characteristics include the ability to provide proper frictional properties for preventing wet brake chatter of oil immersed brakes while simultaneously providing the ability to actuate wet brakes and provide power take-off (PTO) clutch performance. A tractor fluid must provide sufficient antiwear and extreme pressure properties as well as water tolerance/filterability capabilities.
The extreme pressure (EP) properties of tractor fluids are demonstrated by the ability of the fluid to pass a spiral bevel test as well as a straight spur gear test. The tractor fluid must pass wet brake chatter tests as well as provide adequate wet brake capacity when used in oil immersed disk brakes which are comprised of a bronze, graphitic composition, asbestos and paper. The tractor fluid must demonstrate its ability to provide friction retention for power shift transmission clutches such as those clutches which include graphitic and bronze clutches.
U.S. Pat. No. 4,783,274 (Jokinen et al, Nov. 8, 1988) is concerned with hydraulic fluids based on oily triglycerides of fatty acids. This reference relates to the need for fluids for hydraulic purposes which are based on renewable natural resources, and which are, at the same time, environmentally acceptable. One such a natural base component for hydraulic fluids would be the oily triglycerides, which are esters of natural fatty acids with straight-chained alkyl, alkenyl, alkylamines and alkatrienyl chains having a length of commonly C.sub.9 -C.sub.22, and of glycerol, which triglycerides have an iodine number illustrating their degree of unsaturation, of at least 50 and not more than 128. The possibilities to make hydraulic fluids by using the said triglycerides as the base component were investigated.
U.S. Pat. No. 3,776,847 (Pearson et al, Dec. 4, 1973) relates to a lubricating oil composition for the hot rolling of metals comprising (a) from about 50 to about 85% by weight of a natural fatty oil, (b) from about 0.1 to about 10% by weight of an alkaline earth metal salt of an oil-soluble sulfonic acid and (c) from about 5 to about 49.9% by weight of a mineral lubricating oil having a viscosity index of at least 50.
U.S. Pat. No. 2,330,773 (Zimmer et al, Sep. 28, 1943) relates to adding to a suitable mineral oil base stock a small amount of a high molecular weight, oxygen-containing polymer which is depolymerizable at high temperature without charring. Small amount of fatty materials may be, and preferably are, also present.
The oxygen-containing polymer should be of a high molecular weight, e.g., at least 1000 and may be 50,000, 100,000, or even considerably higher, although it must not be so high in molecular weight as to be insoluble in the mineral oil base stocks referred to. In general, these polymers are obtained by polymerizing unsaturated monomeric chemical compounds, such as, esters, ethers, acids, etc. A particularly preferred class of polymers are those produced from esters of acrylic acid and alkyl derivatives thereof, such as methacrylic acid containing a methyl substituent in the alpha position, or other higher alkyl groups, such as, ethyl, propyl, etc., in a similar position; these esters should be derived from monohydric alcohols preferably containing more than 4 carbon atoms, such as amyl, hexyl, heptyl, octyl, lauryl, cetyl, octadecyl, etc. Such acrylic compounds contain the group CH.sub.2 --C, and have attached to this latter carbon atom a carboxylic ester group and either a hydrogen or a hydrocarbon group, such as, an alkyl or aryl group.
U.S. Pat. No. 2,389,227 (Wright, Nov. 20, 1945) involves the blending of a viscose hydrocarbon oil, such as a petroleum lubricating oil fraction, with a non-drying viscous oxidized or thickened fatty oil and with a small amount of an oxygen-containing high molecular weight polymer which normally is substantially solid. By a proper selection and proportioning of these ingredients, a blend can be obtained having suitable viscosity and pour point characteristics to assure proper flowing and penetration and which protectively stays on rubbing surfaces under severe operating conditions.
U.S. Pat. No. 2,413,353 (Hunter et al, Dec. 31, 1946) relates to improved cutting oil compositions.
Various types of fixed fatty oils may be used in the cutting oil compositions of this reference. These oils are intended primarily to increase the oiliness or lubricity of the resultant composition and are customarily used in amounts corresponding to 0.5 to 15.0 per cent by weight. Lard oil is particularly satisfactory for this purpose. However, other animal oils such as tallow oil, neat's-foot oil, sperm oil, wool oil, whale oil and the like may be used. Also certain fish and vegetable oils may be used. The fish oils are generally less advantageous due to their offensive odor and the vegetable oils are likewise less advantageous because of their tendency to oxidize and form gum at the temperatures encountered in cutting operations. However, by the use of a sufficient amount of oxidation inhibitor this defect may be minimized, and vegetable oils such as olive oil, rapeseed oil, corn oil and castor oil may be used.
U.S. Pat. No. 3,640,860 (Miller, Feb. 8, 1972) is concerned with a lubricating composition suitable for use in the continuous casting of metals. More specifically, this reference is concerned with a composition useful for lubricating the metal-mold interface during the continuous casting of metals, which composition contains both dimer and trimer of an unsaturated fatty acid, a glyceride oil, especially a triglyceride, as a solubilizing agent, and a mineral lubricating oil component low in carbon residue and aromatic carbon content. The mineral lubricating oil can be made by a two-state catalytic hydrogenation process.